Inertia switch with magnetic shunting



Aug. 5, 1969 M. FISCHER INERTIA SWITCH WITH MAGNETIC SHUNTING Filed Jan. 16. 1968 mvsm'on MURRY FISCHER HIIIII" L ATTORNEY;

United States Patent 3 459 911 INERTIA SWITCH WITH MAGNETIC SHUNTING Murry Fischer, Spring Valley, N.Y., assignor to Inertia figwitfih, Inc., New York, N.Y., a corporation of New Filed Jan. 16, 1968, Ser. No. 698,170 Int. Cl. H01h 35/02 US. Cl. ZOO-61.45 Claims ABSTRACT OF THE DISCLOSURE The disclosure describes an inertia operated switch in Which is a magnetic ball held in a magnetic field and displaced therefrom when a force is applied to the switch. The switch has a plurality of switch contacts including springy magnetic reeds disposed in the magnetic field including the magnetic ball. The magnetic reeds are deflected laterally by the magnetic field. When the ball is displaced the magnetic field aifecting the magnetic reeds contracts. The reeds are then magnetically released and move laterally with respect to their associated stationary contacts. Replacement of the ball in its initial position restores the magnetic reeds to their magnetically deflected state.

This invention concerns an improved magnetic inertia switch. The invention involves improvements over the inertia switch described in US. Patent No. 2,890,303, issued to S. P. Clurman. In the prior inertia switch, a magnetic steel ball is disposed in a casing and held at one point in a magnetic field maintained by a permanent magnet. The ball is displaced by application of an aceelerating or decelerating force to the switch. The ball moves to a position where it bridges a pair of electrical contacts in a circuit. The casing may be one of the circuit terminals. This type of switch has proven very successful for applications to which it is adapted. However its particular structure limits the scope of applications in which it can be used.

The present invention has as its principal object to provide a magnetic inertia switch of the general type described above, but adapted to open or close a plurality of associated electric circuits without placing the magnetic ball or any part of its casing in any one of the associated switching circuits controlled by the displaced ball.

According to the invention, one or more springy, laterally movable magnetic reed contacts with associated pairs of laterally spaced stationary contacts are disposed circumferentially around a casing containing a movable magnetic ball. The ball itself serves as a part of a magnetic circuit which is expanded to include the magnetic reed contacts. When the ball is displaced, the magnetic field contracts away from the magnetic reed contacts which then move to open or close their associated fixed contacts depending on their electrical arrangement. The invention makes it possible to control one, two, three, four or more circuits external to the inertial assembly comprising the magnetic ball, its casing and a permanent magnet in the casing. The invention further makes it possible to increase or decrease the number of switch operated circuits controlled by the inertial assembly without involving the inertial assembly or the magnetic ball electrically with the switch operated circuits.

The invention will be further explained in detail in connection with the drawing, wherein:

FIG. 1 is an end elevational view of an inertia switch embodying the inventiton.

FIG. 2 is a longitudinal central sectional view on an enlarged scale taken on line 22 of FIG. 1, showing the ball in an initial position in the inertial assembly.

FIG. 3 is a cross sectional view taken on line 3-3 of FIG. 2.

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FIG. 4 is a further enlarged fragmentary sectional view taken on line 44 of FIG. 2.

FIG. 5 is a view similar to FIG. 2, showing the ball in displaced position.

FIG. 6 is a fragmentary sectional view similar to FIG. 4, taken on line 6-6 of FIG. 5.

FIG. 7 is an end view of another inertia switch embodying another form of the invention.

FIG. 8 is an enlarged fragmentary sectional view taken on line 88 of FIG. 7.

Referring first to FIGS. 1-5, the magnetic switch 10 has an inertial assembly 12 comprising a metal cylinder 14. The cylinder is secured at one end to a cylindrical metal block 16. Both the cylinder and block are made of nonmagnetic metal but they could be made of rigid, shock resistant plastic material. The block 16 has a threaded bore 18 in which is fitted an adjustable threaded nonmagnetic plug 20. An external groove 22 in the outer end of the plug permits the plug to be engaged by a tool and axially advanced or retracted in bore 18 when the plug is turned. Secured to the plug and movable therewith is a highly magnetized permanent bar magnet 24. This mag net is slidably disposed in bore extension 18' and can advance or retract axially of the plug while being guided by bore extension 18. The inner end wall 25 of the block is closed.

In cylindrical compartment 25 of cylinder 14 is a ball 26 made of magnetic iron or steel. The ball itself is not a magnet, but is temporarily magnetized only when in the field F of the bar magnet. The magnetic field extends radially outward of the cylinder 14 as indicated by dotted lines in FIG. 2. To the extent described, the structure resembles that of prior Patent 2,890,303 referred to above.

Now according to the invention, a plug 30 is adjustably inserted in the other end of cylinder 14. This plug is sealed to the cylinder by a resilient O-ring 32 disposed in circumferential groove 33. The interior of the cylinder is filled with an inert gas of predetermined composition and at a set pressure through a stem 34 which extends through axial bore 36 in the plug 30. The stem is pinched at its outer end and sealed by solder 38 after the air is exhausted from the cylinder and after the cylinder is refilled with the desired gas. An inert gas such as nitrogen has proven satisfactory for this purpose. The gas provides damping or mechanical resistance to displacement of the ball, thus making the use of springs or other auxiliary mechanical dampers unnecessary. For proper operation the diameter of the ball must be only slightly smaller than the internal diameter of cylinder 14.

Cylinder 14 is wholly or partially embedded in a block 40 made of molded plastic material. In this block are magnetic switch contact assemblies 42. Each assembly 42 includes an electrically nonconductive closed nonmagnetic tube 44 disposed in a recess 46. Tube 44 can be made of glass or plastic material. The tubes all extend parallel to the axis of cylinder 14 and are displaced radially therefrom. Each tube may have indentations which help lock the tube in block 40. Each tube contains a movable magnetic reed 48 secured in one end of the tube and having a laterally movable free end. Reed 48 is electrically continuous with external lead wire 50. Wire 50 extends out of one end 51 of the block 40. Each assembly 42 further includes two other nonmagnetic, electrically conductive strip contacts 52, 54 disposed at opposite sides of the reed 48 and spaced laterally therefrom. Contacts 52, 54 extend out of the tubes and other end of block 40.

In the absence of any applied magnetic field, the outer contact 52 of each assembly 42 is in contact with associated reed contact 48 which is then spaced laterally from inner contact 54 as clearly shown in FIG. 6. When ball 26 is disposed in its initial position shown in FIG. 2,

3 the magnetic field F is diverted or shunted via the ball and across the switch contact assemblies 42. This causes the reed contacts to be drawn inwardly laterally toward the ball so that the reed contacts are in direct electrical and mechanical contact with inner contacts 54; see FIG. 4.

When the switch is displaced by a suflicient axially directed force in direction D, the ball 26 will roll to the other end of cylinder 14 and will be stopped at plug 30; see FIG. 5. The magnetic field P will retract or contract clear of the magnetic reeds 48 which will then return to contact with contacts 52, due to the inherent springiness in the reed contacts. The switch 10 can be reset by turning the switch to an axially upright position to restore the ball to its seat at wall of the plug where the magnetic field F holds the ball in place awaiting another cycle of operation. If the field F is strong enough, it can serve to return the ball 26 to its initial position automatically after the displacing force ceases.

It will be apparent that the ball 26 itself does not act as an electrical circuit member and it is electrically independent of any electric circuits in which contacts 50, 52 and 54 may be connected. If it is necessary to shield the switch 10 from external magnetic fields the block 40 can be partially or wholly enclosed in such a shield as described further below.

FIG. 7 shows another switch 10A which is similar to switch 10 and has basically the same construction with corresponding parts identically numbered. In switch block 40a is a multiplicity of switch contact assemblies 42 disposed circumferentially around the inertial assembly 12. A magnetic shield 60 surrounds cylindrical block 40a to shield the magnetic reeds of the contact assemblies from any external or ambient magnetic field which might otherwise tend to affect or interfere with proper operation of the switch 10A. The block 40 of switch 10 could be cylindrical like block 40a instead of rectangular as shown in FIGS. 1 and 3, and could be protected by a peripheral shield like shield 60 from ambient magnetic fields.

The recesses 46a in which assemblies 42a are inserted in block 49a can be performed with open ends 47 as best shown in FIG. 8. These recesses can then be filled with any one or more of assemblies 42a as desired with one assembly 42a to each recess. As one example, assemblies 10A has seven contact assemblies 42a with one reserve recess 46a left unfilled.

If any contact assembly becomes faulty in operation or if it becomes necessary to replace it for any reason, it can be extracted from its recess 46a and replaced with another one. The recesses 46 of block 40 in switch 10 can be similarly formed with multiple recesses. Tubes 44a may be rectangular or noncircular in form to prevent their turning in recesses 46a. Tubes 44 of assemblies 42a can also be noncircular in cross section.

While only a limited number of embodiments of the invention have been disclosed it will be apparent that many modifications are possible without departing from the invention as defined by the scope of the appended claims.

What is claimed is:

1. A magnetic inertia switch, comprising a hollow nonmagnetic body; a magnet in said body maintaining a permanent magnetic field; a magnetic ball in said body held magnetically in an initial rest position in said field and being displaceable upon application of a force to the ball; a springy, electrically conductive, magnetic reed contact disposed adjacent to and laterally of said body, said ball causing said magnetic reed contact to move in part and deflect laterally against its own spring bias toward said body while in said magnetic field; at least one stationary electrical contact disposed adjacent to the magnetic reed contact at one side thereof for contact by the magnetic reed contact; and support means holding the magnetic reed contact and stationary contact in position laterally of said body, said ball also causing the magnetic field to shift with respect to the magnetic reed contact when the ball is displaced from said initial position in said body upon the application of a force to the ball, so that the magnetic reed contact moves laterally due to its inherent spring bias with respect to the adjacent stationary electrical contact.

2. A magnetic inertia switch as recited in claim 1, wherein said body includes a cylindrical casing having a closed cylindrical compartment in which the ball moves when displaced, and wherein said magnetis a cylindrical bar magnet located at one end of the casing outside of i said compartment, said compartment being filled with a gas of predetermined composition at predetermined pressure to provide mechanical resistance of predetermined magnitude to movement by said ball.

3. A magnetic inertia switch as recited in claim 1, further comprising another stationary electrically conductive contact disposed laterally of the magnetic reed contact at the other side thereof, so that the magnetic reed contact contacts said one stationary contact when the magnetic reed contact is deflected laterally by the magnetic field, and so that the magnetic reed contact contacts the other stationary contact when the magnetic field shifts to release the magnetic reed contact upon displacement of the ball from its initial position.

4. A magnetic inertia switch as recited in claim 3, further comprising a magnetic shield around said support means to shield the magnetic reed contact and said mag netic ball from ambient magnetic fields.

5. A magnetic inertia switch as recited in claim 2, wherein said support means is a nonmagnetic block surrounding the casing, and wherein the block has a recess extending parallel to the central axis of the casing; and a nonmagnetic tube in said recess, said magnetic reed contact and said stationary contact being disposed in said tube.

6. A magnetic inertia switch as recited in claim 5, further comprising another stationary electrically conductive contact disposed laterally of the magnetic reed contact at the other side thereof in said tube, so that the magnetic reed contact contacts said one stationary contact when the magnetic reed contact is deflected laterally by the magnetic field, and so that the magnetic reed contact contacts the other stationary contact when the magnetic field shifts to release the magetic reed contact upon displacement of the ball from its initial position.

7. A magnetic inertia switch as recited in claim 6, wherein said block has at least one other recess therein extending parallel to the central axis of the casing; another nonmagnetic tube in said other recess; another springy, electrically conductive, magnetic reed contact in said other tube held at one part thereof so that another part is moveable laterally, said other magnetic reed contact being disposed in said magnetic field and held deflected laterally thereby when the magnetic ball is in its initial position; and a pair of other stationary electrically conductive contacts in said other tube respectively disposed on opposite sides of said other magnetic reed contact, so that the other magnetic reed contacts one of said pair of stationary contacts when the other magnetic reed contact is deflected laterally by the magnetic field, and so that the other magnetic reed contact contacts the other staionary contact of said pair of contacts when the magnetic field shifts to release the other magnetic reed contact.

8. A magnetic inertia switch as recited in claim 7, further comprising a magnetic shield around said block to shield the magnetic reed contacts and the magnetic ball from ambient magnetic fields.

9. A magnetic inertia switch as recited in claim 7, wherein each of the stationary contacts and each of the magnetic reed contacts has an end portion extending outwardly of the block for connection in electrical circuits external of and independent of the magnetic ball and said casing.

10. A magnetic inertia switch as recited in claim 7, wherein each recess in the block is open at one end to 5 6 facilitate insertion of a said tube in the recess and removal of the tube from the recess, ROBERT K. SCHAEFER, Primary Examiner References Cited M. GINSBURG, Assistant Examiner UNITED STATES PATENTS US. Cl. X.R.

5 2,976,378 3/1961 Goddard 200-61.45 335-205 3,011,036 11/1961 La Rocca 335-205 

